Add support for loading extensions (issue #1947)

- Add CefRequestContext::LoadExtension, CefExtension, CefExtensionHandler and
  related methods/interfaces.
- Add chrome://extensions-support that lists supported Chrome APIs.
- Add CefBrowserHost::SetAutoResizeEnabled and CefDisplayHandler::OnAutoResize
  to support browser resize based on preferred web contents size.
- views: Add support for custom CefMenuButton popups.
- cefclient: Run with `--load-extension=set_page_color` command-line flag for
  an extension loading example. Add `--use-views` on Windows and Linux for an
  even better example.

libcef_dll/ctocpp/views/window_delegate_ctocpp.h

@@ -9,7 +9,7 @@
 // implementations. See the translator.README.txt file in the tools directory
 // for more information.
 //
-// $hash=d6154885643d45eb81ecbd3a017776983a841651$
+// $hash=9eb43c9bb618484946e6915808822b1af7ad2258$
 //
 
 #ifndef CEF_LIBCEF_DLL_CTOCPP_VIEWS_WINDOW_DELEGATE_CTOCPP_H_
@@ -38,6 +38,9 @@ class CefWindowDelegateCToCpp
   // CefWindowDelegate methods.
   void OnWindowCreated(CefRefPtr<CefWindow> window) override;
   void OnWindowDestroyed(CefRefPtr<CefWindow> window) override;
+  CefRefPtr<CefWindow> GetParentWindow(CefRefPtr<CefWindow> window,
+                                       bool* is_menu,
+                                       bool* can_activate_menu) override;
   bool IsFrameless(CefRefPtr<CefWindow> window) override;
   bool CanResize(CefRefPtr<CefWindow> window) override;
   bool CanMaximize(CefRefPtr<CefWindow> window) override;